Brain surgery is an increasingly common and effective treatment for intractable epilepsy. Successful surgical outcome depends on correctly identifying a brain locus of seizure origin and minimizing resection of important functional areas in the brain, yet current invasive techniques for accomplishing these goals add to the risk and cost of surgical treatment. The goal of this research program is to quantitatively assess the value of functional magnetic resonance imaging (FMRI) in the presurgical assessment of patients with epilepsy. The first specific aim is to test whether FMRI can replace the intracarotid amobarbital (Wada) test used for determining lateralization of language and memory functions. The level of agreement between the two tests, their relative reliability, and the power of each in predicting cognitive outcome will be precisely measured. The second aim is to assess the predictive value of FMRI for neurosurgical planning. The volume of resected functional and nonfunctional tissue in operated patients, as defined by preoperative FMRI maps and quantitative anatomical MRI, will be correlated with the appearance of postoperative language and memory deficits, postoperative seizure control, and quality of life measures to determine the potential of FMRI to help define optimal resection boundaries. The final specific aim is to test the capability of FMRI in predicting seizure lateralization and seizure control outcome in patients with temporal lobe epilepsy. Lateralization of temporal lobe functional activation by FMRI will be used as an indicator of seizure focus lateralization. The predictive power of this FMRI index will be compared to standard techniques for seizure focus identification, including noninvasive and intracranial EEG, routine and volumetric MRI, psychometric testing, SPECT, and the Wada test. In accomplishing these aims, a basis will be established for using FMRI to reduce the morbidity and to increase the effectiveness of epilepsy surgery.